KR102648974B1 - Graphene Oxide And Method for Manufacturing Of The Same, Display Device Comprising The Same - Google Patents

Abstract

The present invention provides graphene oxide with excellent transmittance and electrical properties by manufacturing graphene oxide with oxidized edges. Graphene oxide according to an embodiment of the present invention has its edges oxidized and the layers are separated with oxygen atoms. Graphene oxide is in the shape of a sheet.

Description

Graphene oxide and its manufacturing method, display device comprising the same {Graphene Oxide And Method for Manufacturing Of The Same, Display Device Comprising The Same}

The present invention relates to graphene oxide, a method of manufacturing the same, and a display device including the same.

Graphene is one of the allotropes of carbon, and is a two-dimensional structure with a single atomic layer thickness in which carbon atoms are each connected by sp2 bonds, and benzene-type carbon rings are connected to form a honeycomb crystal.

A total of four methods are known to produce graphene: mechanical exfoliation, chemical vapor deposition (CVD), organic solvent method, and graphite oxidation-reduction method. Among these, the graphite oxidation-reduction method is used in large quantities. It is most preferred in terms of ease of production.

The oxidation-reduction method of graphite is to reduce the pi electron density between layers by inducing oxygen-based functional groups, thereby lowering the van der Waals attraction to facilitate separation between layers. To date, methods for oxidizing graphite include Hummers. ) method, Staudenmaier method, Brodie method, etc. are mainly known.

However, since the above-described oxidation process combines a strong acid and a strong oxidizing agent to oxidize under extreme conditions, the original graphene structure is not restored even after reduction, and oxygen remains after the reduction process, so it is not suitable for mass production of graphene. Although it is easy, it has the disadvantage of not being able to produce high-quality graphene. In addition, generally, in oxidation between graphite layers, hydroxy groups and epoxy groups are first created, and as the oxidation reaction continues, ether, etc. are finally created, and carboxyl groups are created. In this process, the carbon that makes up graphene- Carbon bonds are broken, causing defects, and these are not completely restored even after reduction, causing a problem in that graphene's original electrical properties deteriorate.

The present invention provides graphene oxide with excellent transmittance and electrical properties by manufacturing graphene oxide with oxidized edges.

In order to achieve the above object, the edges of graphene oxide according to an embodiment of the present invention are oxidized and the layers are separated with oxygen atoms. Graphene oxide is in the shape of a sheet.

The method for producing graphene oxide according to an embodiment of the present invention includes a first step of dispersing graphite in a container containing concentrated sulfuric acid and adding water, a second step of oxidizing graphite by adding potassium permanganate to the container, and adding water to the container. It includes a third step of adding hydrogen peroxide to terminate oxidation and washing to obtain graphite with oxidized edges, and a fourth step of peeling the obtained graphite between layers to obtain graphene oxide with oxidized edges.

The water is added so that the content ratio of graphite to water is 1:13 to 1:20.

By adding water, concentrated sulfuric acid changes to dilute sulfuric acid, and the concentration of dilute sulfuric acid is 50% to 60%.

Additionally, a display device according to an embodiment of the present invention includes a substrate, a thin film transistor, and a pixel electrode. A thin film transistor is disposed on a substrate and includes an active layer, a gate electrode, a source electrode, and a drain electrode. The pixel electrode is connected to a thin film transistor and includes graphene oxide whose edges are oxidized and exfoliated with oxygen atoms.

Graphene oxide is in the form of a sheet.

It further includes a light-emitting layer positioned on the pixel electrode, an opposing electrode positioned on the light-emitting layer, an encapsulation layer positioned on the opposing electrode, and a cover window positioned on the encapsulation layer.

It further includes a common electrode positioned spaced apart from or below the same plane as the pixel electrode, and a liquid crystal layer positioned on the common electrode.

Graphene oxide and its production method according to an embodiment of the present invention slow the oxidation reaction of graphite by adding water to concentrated sulfuric acid to break the concentrated sulfuric acid conditions in advance. Therefore, graphene oxide with oxidized edges can be obtained.

In addition, the edge-oxidized graphene oxide of the present invention has the advantage of excellent transmittance and electrical conductivity as a thin film.

Figure 1 is a schematic diagram of graphene oxide of the present invention.
Figure 2 is a diagram showing the method for producing graphene oxide according to the present invention by process.
Figure 3 is a diagram showing the structure of graphite for each manufacturing process of the present invention.
Figure 4 is a cross-sectional view showing a liquid crystal display device according to an embodiment of the present invention.
Figure 5 is a cross-sectional view showing an organic light emitting display device according to another embodiment of the present invention.
Figure 6 is a graph showing Raman results of graphite manufactured according to Comparative Example 1.
Figure 7 is a diagram showing Raman results of graphene oxide prepared according to Comparative Example 2.
Figure 8 is a diagram showing Raman results of graphene oxide prepared according to an example.
Figure 9 is a graph showing the XPS results of graphite and graphene oxide prepared according to Comparative Examples 1 and 2 and Examples.
Figure 10 is a graph showing FTIR results of graphite and graphene oxide prepared according to Comparative Examples 1 and 2 and Examples.
Figure 11 is a graph showing the TGA results of graphite and graphene oxide prepared according to Comparative Examples 1 and 2 and Examples.
Figure 12 is a diagram showing the TEM measurement results of graphene oxide prepared according to Comparative Example 2.
Figure 13 is a diagram showing the TEM measurement results of graphene oxide prepared according to an example.
Figure 14 is a graph showing sheet resistance measured according to transmittance of graphene oxide thin films manufactured according to Comparative Example 2 and Examples.

Hereinafter, some embodiments of the present invention will be described in detail through illustrative drawings. When adding reference numerals to components in each drawing, it should be noted that identical components are given the same reference numerals as much as possible even if they are shown in different drawings. Additionally, when describing embodiments of the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description will be omitted.

Additionally, when describing the components of the invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish the component from other components, and the nature, order, or order of the component is not limited by the term. When a component is described as being “connected,” “coupled,” or “connected” to another component, that component may be directly connected or connected to that other component, but there is another component between each component. It will be understood that elements may be “connected,” “combined,” or “connected.” In the same context, when a component is described as being formed “on” or “under” another component, that component means that it is formed directly on that other component or indirectly through another component. It should be understood as including.

The display device according to the present invention disclosed below may be an organic light emitting display device, a liquid crystal display device, an electrophoretic display device, etc. In the present invention, a liquid crystal display device is explained as an example. A liquid crystal display device consists of a thin film transistor array substrate with a pixel electrode and a common electrode formed on a thin film transistor, a color filter substrate, and a liquid crystal layer sandwiched between the two substrates. In this liquid crystal display device, the common electrode and the pixel electrode are positioned vertically or The liquid crystal is driven by a horizontal electric field. Additionally, the display device according to the present invention can also be used in an organic light emitting display device. For example, an organic light emitting display device includes a first electrode connected to a thin film transistor, a second electrode, and a light emitting layer made of organic material between them. Therefore, holes supplied from the first electrode and electrons supplied from the second electrode combine in the light emitting layer to form excitons, which are hole-electron pairs, and emit light by the energy generated when the excitons return to the ground state. The graphene oxide of the present invention, which will be described later, can be used in the pixel electrode of the above-described display device.

Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.

The present invention discloses partially oxidized graphene oxide and a method for manufacturing the same, and a thin film transistor array substrate and display device including electrodes using the same. Figure 1 is a schematic diagram of graphene oxide of the present invention.

partially oxidized graphene oxide

The graphene oxide of the present invention is graphene oxide that has oxygen atoms at the edges and is exfoliated from layer to layer. This graphene oxide is peeled off between layers to form a sheet.

Referring to Figure 1, in the graphene oxide of the present invention, carbon is combined in a honeycomb structure to form a single sheet-shaped graphene oxide. The edges of each graphene oxide are partially oxidized by combining oxygen atoms that appear red at the edges. In other words, oxygen atoms do not exist on the surface of the graphene oxide because it is not oxidized, and the edges of the graphene oxide are oxidized and oxygen atoms are combined. That is, the graphene oxide of the present invention may be graphene oxide whose edges are oxidized.

Graphene oxide with oxidized edges of the present invention not only exhibits the natural electrical properties of graphene even after reduction and can be used as electrodes for electrical devices such as capacitor electrodes, transistor electrodes, and display electrodes, but also exhibits transparency and is used in the field of transparent electrodes. It is also possible to use . In addition, the graphene oxide with oxidized edges of the present invention can be included in the active layer of a thin film transistor and used to improve mobility.

oxidized edges graphene of oxide Manufacturing method

Graphene oxide with oxidized edges of the present invention can be partially oxidized only at the edges through a partial oxidation process, unlike the generally known oxidation-then-reduction method.

Figure 2 is a diagram showing the manufacturing method of graphene oxide of the present invention for each process, and Figure 3 is a diagram showing the structure of graphite for each manufacturing process of the present invention.

The partially oxidized graphene oxide of the present invention can be manufactured through a four-step manufacturing method as follows. The first step is to disperse graphite in a container containing concentrated sulfuric acid and add water, the second step is to oxidize the graphite by adding an oxidizing agent to the container, the oxidation is completed by adding hydrogen peroxide to the container, and the edges are partially oxidized by washing. It can be manufactured including a third step of obtaining graphene oxide, and a fourth step of peeling the obtained graphene oxide between layers.

The method for producing partially oxidized graphene oxide of the present invention will be described with reference to FIGS. 2 and 3 as follows.

<S1> Add graphite and water sequentially to concentrated sulfuric acid.

<S2> Adding an oxidizing agent to graphite.

<S3> Add hydrogen peroxide to graphite and wash it to obtain graphene oxide with oxidized edges.

<S4> Delamination of graphene oxide.

Hereinafter, the method for producing graphene oxide of the present invention will be described in more detail as follows.

first stage <S1>

Graphite used as a starting material may be natural graphite, Kish graphite, synthetic graphite, expanded graphite or expanded graphite, or a mixture thereof.

Since the subsequent reaction between graphite and the oxidizing agent is preferably performed in the presence of acid, sulfuric acid, nitric acid, phosphoric acid, or carboxylic acid can be used as the graphite-containing solution.

In the present invention, water is added to the graphite-containing solution. Unlike the conventional hummus method, which uses concentrated sulfuric acid with a concentration of 95% to 98%, the concentrated sulfuric acid condition is broken by adding water and changed to dilute sulfuric acid condition. For example, the concentration of dilute sulfuric acid may be 50% to 60% concentration.

In this step, the content of water varies depending on the graphite content, and the content ratio of graphite to water can be added at a ratio of 1:13 to 1:20. In this case, the content is in volume %. Here, if the content ratio of graphite and water is 1:13 or more, the oxidation reaction can be slowed by changing the concentrated sulfuric acid to dilute sulfuric acid conditions to oxidize the edges of the graphite, and some of the manganese heptaoxide described later may remain on the surface of the graphite. This can prevent oxidation from occurring. If the content ratio of graphite and water is less than 1:20, the dispersion of graphite decreases rapidly, preventing the oxidation reaction from occurring efficiently.

Water is added while maintaining the temperature of the graphite-containing solution below 70 degrees.

Second step <S2>

This step is to oxidize the previously prepared solution by adding an oxidizing agent.

The oxidizing agent used in the present invention may include, for example, a component selected from the group consisting of permanganic acid, chloric acid, or a combination thereof. For example, the oxidizing agent may include potassium permanganate, calcium permanganate, ammonium permanganate, sodium permanganate, potassium chlorate, sodium chlorate, ammonium chlorate, or mixtures thereof.

When potassium permanganate is added under diluted sulfuric acid conditions, manganese heptaoxide is produced and the reverse reaction occurs in which manganese heptaoxide reacts with water to return to permanganate ion (MnO ₄ -). Permanganate ions are less powerful than manganese heptaoxide, so they cannot attack the basal plane of graphite, so oxidation begins at the edges of graphite, which are relatively highly reactive.

The reaction time is slow for up to 24 hours, and the temperature of the reaction tank is 70 degrees.

Step 3 <S3>

In this step, the oxidation reaction is terminated by adding a reaction terminating agent. Hydrogen peroxide (H ₂ O ₂ ) can be used as a reaction terminating agent. When permanganate ion encounters hydrogen peroxide, it changes into manganese ion and loses its oxidizing power. In other words, hydrogen peroxide plays a role in ending oxidation.

The content of hydrogen peroxide is added in a certain ratio to the graphite content. By adding graphite to hydrogen peroxide in a content ratio of 1:5 or more, the oxidation reaction can be completely terminated.

Afterwards, to remove and neutralize foreign ions, it is centrifuged and washed three times with hydrochloric acid and five times with distilled water. Accordingly, graphite with oxidized edges is obtained.

Step 4 <S4>

The edge-oxidized graphite obtained through the previous step is subjected to interlayer exfoliation to obtain individual edge-oxidized graphene oxides. Delamination may be performed using a homogenizer, Couette-Taylor reactor, high pressure homogenizer, ultrasonicator, or a combination thereof.

After the above peeling step, washing and separation steps of graphene oxide may be additionally performed. Washing and separation can be performed using a filter press, centrifuge, decanter, or a combination of these.

According to the manufacturing method of the present invention, the oxidation reaction of graphite is slowed by adding water to concentrated sulfuric acid to break the concentrated sulfuric acid condition in advance. Therefore, graphene oxide with oxidized edges can be obtained.

The graphene oxide with oxidized edges of the present invention described above can be used in pixel electrodes of thin film transistor array substrates and display devices including the same. In the following, a pixel electrode of a thin film transistor array substrate and a display device including the same will be described as an example, but as described above, it can be used as a variety of conductive materials for electrical devices.

thin film transistor Array substrate and display device

FIG. 4 is a cross-sectional view showing a liquid crystal display device according to an embodiment of the present invention, and FIG. 5 is a cross-sectional view showing an organic light emitting display device according to another embodiment of the present invention.

The thin film transistor array substrate disclosed in the present invention is explained as an example of a bottom-gate type thin film transistor in which the gate electrode is located below the active layer. However, the present invention is not limited to this, and the structure of all known thin film transistors, such as a top-gate type thin film transistor in which the gate electrode is located above the active layer, can be applied.

Referring to FIG. 4, the gate electrode 120 is located on the substrate 110. The substrate 110 is made of transparent or opaque glass, plastic, or metal. The gate electrode 120 is made of copper (Cu), molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and tantalum (Ta). and tungsten (W), or an alloy thereof. A gate insulating film 130 that insulates the gate electrode 120 is located on the gate electrode 120. The gate insulating film 130 is made of a silicon oxide film (SiOx), a silicon nitride film (SiNx), or a multilayer thereof.

The active layer 140 is located on the gate insulating film 130. The active layer 140 includes amorphous silicon, polycrystalline silicon, an oxide semiconductor, a carbon allotrope, or a mixture thereof. A source electrode 150a contacting one side of the active layer 140 and a drain electrode 150b contacting the other side of the active layer 140 are located on the active layer 140. The source electrode 150a and the drain electrode 150b may be made of a single layer or multiple layers. In the case of a single layer, molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), It may be made of any one selected from the group consisting of nickel (Ni), neodymium (Nd), and copper (Cu), or an alloy thereof. In addition, when the source electrode 150a and the drain electrode 150b are multilayered, they are a double layer of molybdenum/aluminum-neodymium, molybdenum/aluminum, or titanium/aluminum, or a double layer of molybdenum/aluminum-neodymium/molybdenum, molybdenum/aluminum/molybdenum, or titanium. It can be made of a triple layer of /aluminum/titanium.

An organic insulating film 160 is located on the source electrode 150a and the drain electrode 150b. The organic insulating film 160 is used to flatten the lower step and may be made of organic materials such as photo acryl, polyimide, benzocyclobutene resin, or acrylate. there is. The organic insulating film 160 includes a via hole 165 exposing the drain electrode 150b. Although not shown, a passivation film made of silicon oxide (SiOx), silicon nitride (SiNx), or a multilayer thereof may be positioned on the source electrode 150a and the drain electrode 150b.

The pixel electrode 170 and the common electrode 180 are located on the organic insulating film 160. The pixel electrode 170 is connected to the drain electrode 150b through the via hole 165 formed in the organic insulating film 160. The pixel electrode 170 and the common electrode 180 may be made of graphene oxide according to the present invention. The graphene oxide of the present invention has excellent electrical conductivity and transparency, so it can be used as a pixel electrode. The pixel electrode 170 and the common electrode 180 are arranged alternately to form a horizontal electric field between the pixel electrode 170 and the common electrode 180.

An upper substrate 190 is located opposite to the substrate 110, and a liquid crystal layer (LC) is located between the substrate 110 and the upper substrate 190. In the embodiment of the present invention, an in-plane switching (IPS) liquid crystal display device in which the pixel electrode 170 and the common electrode 180 are located on the same plane is described as an example. However, the present invention is not limited to this, and the common electrode 180 may be located below the pixel electrode 170, or the common electrode 180 may be located on the upper substrate 190.

Meanwhile, referring to FIG. 5, the display device of the present invention may be an organic light emitting display device including an organic light emitting diode. In more detail, the organic insulating film 160 is located on the source electrode 150a and the drain electrode 150b. The organic insulating film 160 includes a via hole 165 exposing the drain electrode 150b.

The pixel electrode 170 is located on the organic insulating film 160. The pixel electrode 170 is connected to the drain electrode 150b through the via hole 165 formed in the organic insulating film 160. The pixel electrode 170 may be made of graphene oxide of the present invention. The graphene oxide of the present invention has excellent electrical conductivity and transparency, so it can be used as a pixel electrode.

The bank layer 175 is located on the pixel electrode 170. The bank layer 175 may be a pixel defining layer that exposes a portion of the pixel electrode 170 to define a pixel. The organic layer 190 is located on the bank layer 175 and the exposed pixel electrode 170. The organic layer 190 includes a light emitting layer that emits light by combining electrons and holes, and may include a hole injection layer, a hole transport layer, an electron transport layer, or an electron injection layer. The counter electrode 200 is located on the substrate 110 on which the organic layer 190 is formed. The counter electrode 200 is a cathode electrode and may be made of magnesium (Mg), calcium (Ca), aluminum (Al), silver (Ag), or an alloy thereof with a low work function. Accordingly, an organic light emitting diode (OLED) including a pixel electrode 170, an organic layer 190, and a counter electrode 200 is configured.

The encapsulation layer 210 is located on the substrate 110 on which the organic light emitting diode (OLED) is formed. The encapsulation layer 210 encapsulates the substrate 110 including the underlying organic light emitting diode (OLED) and may be made of an inorganic film, an organic film, or a multilayer structure thereof. A cover window 220 is located on the encapsulation layer 210 to form an organic light emitting display device.

Hereinafter, experimental examples of graphene oxide according to embodiments of the present invention will be disclosed. The following experimental example is only an example of the present invention and the present invention is not limited thereto.

Experiment 1: Edge oxidized graphene oxide proof

Comparative example One

Graphite as a starting material was prepared.

Comparative example 2

Fully oxidized graphene oxide was prepared using the Hummers method.

Example

Using a low-temperature reaction tank, mix 3 g of graphite with 148 ml of concentrated sulfuric acid, lowered to 0°C at 300 rpm, and slowly add 50 ml of distilled water using a burette so that the temperature does not exceed 70°C. Afterwards, 18 g of permanganic acid mixed in 250 ml of distilled water was slowly added, the temperature of the reaction tank was raised to 70°C, and the reaction was allowed to proceed for up to 24 hours. Afterwards, 10 ml of 30% hydrogen peroxide was added to terminate the reaction, and then centrifuged at 4000 rpm three times for 15 minutes each with 1 M hydrochloric acid and five times for 30 minutes each with distilled water to obtain oxidized graphite (EOG). The obtained edge graphite oxide is mixed with 0.1M sodium hydroxide for more than 12 hours and then exfoliated by injecting ultrasonic waves for 6 hours using a water tank type ultrasonic generator. The exfoliated edge graphene oxide (LPEOG) dispersion is obtained by removing the supernatant three times at 4000 rpm for 1 hour. The obtained edged graphene oxide dispersion was dialyzed against distilled water more than 10 times to bring the pH close to neutral and remove sodium hydroxide to prepare edged graphene oxide.

Graphite and graphene oxide prepared according to the above-mentioned Comparative Examples 1 and 2 and Examples were analyzed by Raman, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). Figure 6 is the Raman result of graphite prepared according to Comparative Example 1, Figure 7 is the Raman result of graphene oxide prepared according to Comparative Example 2, and Figure 8 is the Raman result of graphene oxide prepared according to Example. , Figure 9 is the XPS results of graphite and graphene oxide prepared according to Comparative Examples 1 and 2 and Examples, and Figure 10 is the FTIR result of graphite and graphene oxide prepared according to Comparative Examples 1 and 2 and Examples. , Figure 11 is the TGA results of graphite and graphene oxide prepared according to Comparative Examples 1 and 2 and Examples. (In FIGS. 9 to 11, Examples #1, #2, and #3 refer to graphene oxide prepared according to each example.) Figure 12 is a TEM measurement of graphene oxide prepared according to Comparative Example 2. This is the result, and Figure 13 is the TEM measurement result of graphene oxide prepared according to the example.

First, referring to FIG. 6, it was confirmed that the graphite of Comparative Example 1 had a crystallinity of less than 0.1 on both the basal plane and the edge and was not oxidized. Referring to FIG. 7, it was confirmed that the fully oxidized graphene oxide of Comparative Example 2 was oxidized to a crystallinity of 1 or more on both the base and the edges. Referring to FIG. 8, the edge-oxidized graphene oxide of the example showed a basal plane crystallinity of 0.33 and an edge crystallinity of 1.08. In other words, it was confirmed that the edge was oxidized and the base surface was not oxidized compared to Comparative Example 2.

Referring to (a) of Figure 9, Comparative Example 1 showed a very high C-C and C=C carbon bond ratio of 91%, confirming that it was not oxidized. In Comparative Example 2, the C-C and C=C carbon bond ratio was 51.6%, and the remaining oxygen bond ratio of C-0H, C-O-C, C=O, and C-OOH was 48.4%, confirming that it was about half oxidized. Examples #1 to #3 have C-C and C=C carbon bond ratios of 72.1%, 69.5%, and 66.8%, respectively, and oxygen bond ratios of C-0H, C-O-C, C=O, and C-OOH of 27.9% and 30.5, respectively. %, 33.2%, confirming that part of it was oxidized. Referring to (b) of FIG. 9, in Comparative Example 1, the number of carbon atoms divided by the number of oxygen atoms was about 8, confirming that the number of oxygen atoms was so small that it was not oxidized. In Comparative Example 2, the number of carbon atoms divided by the number of oxygen atoms was approximately 2, confirming that the number of oxygen atoms was significantly oxidized. In the example, the number of carbon atoms divided by the number of oxygen atoms was approximately 3, confirming that some oxygen atoms were present and some were oxidized.

Referring to FIG. 10, it was confirmed that Comparative Example 1 was not oxidized as no peaks appeared at the wavelengths corresponding to C=O, C-O, C-O-C, and C-OH bonds. Comparative Example 2 showed large peaks at wavelengths corresponding to O-H, C=O, C-O, C-O-C, and C-OH bonds, confirming that it was heavily oxidized. In the example, it was confirmed that some oxidation occurred as peaks appeared small at the wavelengths corresponding to O-H, C=O, C-O, C-O-C, and C-OH bonds.

Referring to Figure 11, Comparative Example 1 showed a weight ratio of about 100% at a temperature of about 300°C, so it was confirmed that it did not decompose at high heat due to no defects such as oxygen and was not oxidized. In Comparative Example 2, the weight ratio was about 60% at a temperature of about 300°C, and it was confirmed that it was decomposed at high heat due to many defects such as oxygen and was greatly oxidized. In the example, the weight ratio was about 90% at a temperature of about 300°C, and it was confirmed that a small amount of defects such as oxygen were present, and some of them were decomposed at high heat and partially oxidized.

Meanwhile, referring to FIG. 12, in Comparative Example 2, no white dots appeared in the TEM image, so it was confirmed that the crystal structure was greatly destroyed, and through this, it was heavily oxidized. Referring to FIG. 13, in the TEM image of the example, many white dots appeared only in the crystal structure, confirming that there was not much oxidation.

Through the results of Experiment 1 described above, it can be confirmed that the graphene oxide prepared according to an example of the present invention was partially oxidized at the edges.

Experiment 2: graphene oxide Measurement of properties of thin films

After reducing the graphene oxides prepared according to the above-described Comparative Example 2 and Example, bulk thin films were prepared, respectively. The sheet resistance according to the transmittance of the graphene oxides prepared in this way was measured and shown in Figure 14.

Referring to FIG. 14, the sheet resistance of the graphene oxide thin film manufactured according to Comparative Example 2 increased significantly as the transmittance increased, showing a sheet resistance of about 100 kΩ/sq at a transmittance of about 90%. On the other hand, the graphene oxide thin film manufactured according to the example did not have a significant increase in sheet resistance even as the transmittance increased, and showed a sheet resistance of about 10 kΩ/sq at a transmittance of about 90%.

Through the results of Experiment 2, it was confirmed that the graphene oxide thin film manufactured according to an example of the present invention had very excellent transmittance and electrical conductivity.

For reference, when the graphene oxides prepared according to Comparative Example 2 and Examples were reduced at about 500 ° C to produce a thin film, the graphene oxide thin film of the Example was about 56% (at 3,470 S/m) compared to Comparative Example 2. increased to 5,440 S/m) and showed improved electrical conductivity characteristics. When thin films were produced by reducing the graphene oxides prepared according to Comparative Example 2 and Examples at about 1100°C, the graphene oxide thin films of Examples had about 70% (68,800 S/m to 120,000 S/m) compared to Comparative Example 2. m) showed improved electrical conductivity characteristics. In addition, when a transparent electrode thin film was manufactured by reducing the graphene oxides prepared according to Comparative Example 2 and Examples at about 1100 ° C., the graphene oxide thin film of Examples had a transmittance of about 80%, which was 41% compared to Comparative Example 2. It showed improved electrical conductivity properties.

In addition, graphene oxide with oxidized edges according to an embodiment of the present invention can be compressed to a high concentration of up to 15.0 mg/ml, and patterning using a brush is possible using this.

As described above, graphene oxide and its manufacturing method according to an embodiment of the present invention slow the oxidation reaction of graphite by adding water to concentrated sulfuric acid to break the concentrated sulfuric acid conditions in advance. Therefore, graphene oxide with oxidized edges can be obtained.

In addition, the edge-oxidized graphene oxide of the present invention has the advantage of excellent transmittance and electrical conductivity as a thin film.

Through the above-described content, those skilled in the art will be able to see that various changes and modifications can be made without departing from the technical idea of the present invention. Therefore, the technical scope of the present invention should not be limited to what is described in the detailed description of the specification, but should be defined by the scope of the patent claims.

110: substrate 120: semiconductor layer
130: gate insulating film 140: gate electrode
150a: source electrode 150b: drain electrode
160: organic insulating film 170: pixel electrode
180: Common electrode LC: Liquid crystal layer

Claims (9)

delete delete A first step of dispersing graphite in a container containing concentrated sulfuric acid and adding water;
A second step of oxidizing the graphite by adding potassium permanganate to the container;
A third step of adding hydrogen peroxide to the container to terminate oxidation and washing to obtain graphite with oxidized edges; and
A fourth step of peeling the obtained graphite from layer to layer to obtain graphene oxide with oxidized edges,
The water is added so that the content ratio of the graphite and the water is 1:13 to 1:20,
A method of producing graphene oxide wherein the concentrated sulfuric acid is changed into dilute sulfuric acid by adding the water, and the concentration of the dilute sulfuric acid is 50% to 60%. delete delete Board;
A thin film transistor disposed on the substrate and including an active layer, a gate electrode, a source electrode, and a drain electrode;
a pixel electrode connected to the thin film transistor and including graphene oxide whose edges are oxidized and have oxygen atoms and are exfoliated between layers; and
An organic insulating film formed on the pixel electrode,
A display device in which the pixel electrode is connected to the drain electrode through a via hole penetrating the organic insulating film. According to clause 6,
The graphene oxide is a display device in the form of a sheet. According to claim 6 or 7,
A light emitting layer located on the pixel electrode;
A counter electrode located on the light emitting layer;
an encapsulation layer located on the opposing electrode; and
A display device further comprising a cover window located on the encapsulation layer. According to claim 6 or 7,
a common electrode positioned spaced apart from or below the same plane as the pixel electrode; and
A display device further comprising a liquid crystal layer located on the common electrode.

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